Control device and spring therefor

Claim 1

A PRESSURE RELIEF VALVE ASSEMBLY CHARACTERIZED BY A STEEP SEAT-LOADING CURVE WHICH IS DISCONTINUOUS AT CRACKING PRESSURE AND BY THE SUBSTANTIAL ABSENSE OF FRICTION AND HYSTERESIS LOSSES, WHICH COMPRISES: A HOUSING HAVING A HOLLOW INTERIOR PROVIDED WITH A FLUID PRESSURE INLET AND A FLUID PRESSURE OUTLET, A VALVE DEVICE NORMALLY DIVIDING THE INTERIOR OF SAID HOUSING INTO TWO SEPARATE CHAMBERS, ONE COMMUNICATING WITH SAID INLET AND THE OTHER WITH SAID OUTLET, AND ADAPTED TO ESTABLISH COMMUNICATION BETWEEN SAID CHAMBERS IN RESPONSE TO FLUID PRESSURE AT SAID INLET EXCEEDING A PREDETERMINED VALUE, SAID VALVE DEVICE INCLUDING A HAT-SHAPED SPRING DIAPHRAGM HAVING A RIM PORTION, A CYLINDRICAL SIDE WALL PORTION EXTENDING FROM SAID RIM PORTION, A CYLINDRICAL COLLAR PORTION DISPOSED CONCENTRICALLY OF SAID SIDE WALL PORTION AT THAT END THEREOF REMOTE FROM SAID RIM PORTION, AND A CROWN PORTION JOINING SAID COLLAR PORTION TO SAID END OF THE SIDE WALL PORTION REMOTE FROM SAID RIM PORTION, SAID RIM PORTION BEING RIGIDLY SECURED TO SAID HOUSING AND CONSTITUTING THE SOLE CONNECTION BETWEEN SAID HOUSING AND SAID VALVE DEVICE, A SEAT MEMBER CARRIED BY SAID COLLAR PORTION, A VALVE MEMBER, RESILIENT MEANS ACTING BETWEEN SAID HOUSING AND SAID VALVE MEMBER FOR NORMALLY SEATING SAID VALVE MEMBER ON SAID SEAT MEMBER AND PERMITTING SAID VALVE MEMBER, WHILE SO